<template>
<div ref="scroll">
  <slot></slot>
</div>
</template>

<script >
import BScroll from 'better-scroll'
const DIRECTION_H = 'horizontal'
const DIRECTION_V = 'vertical'
const MAX_BORDER_NUM = 50
export default {
  props: {
    // 有时候我们需要知道滚动的位置 为 1 的时候，会非实时 probeType 为 2 的时实时的派发 scroll 事件
    probeType: {
      type: Number,
      default: 1
    },
    // 是否需要点击事件
    click: {
      type: Boolean,
      default: false
    },
    // 外部数据
    data: {
      type: Array,
      default: null
    },
    // 是否需要监听滚动底部后派发事件通过
    pullup: {
      type: Boolean,
      default: false
    },
    pullUpLoad: {
      type: Boolean,
      default: false
    },
    // 当前滚动方向
    direction: {
      type: String,
      default: DIRECTION_V
    }
  },
  mounted() {
    // 必须要在mounted钩子初始化 DOM渲染之后 不然报错
    setTimeout(() => {
      this.fnInitScroll()
    }, 20)
  },
  methods: {
    fnInitScroll() {
      if (!this.$refs.scroll) {
        return
      }
      this.scroll = new BScroll(this.$refs.scroll, {
          probeType: this.probeType,
          click: this.click,
          eventPassthrough: this.direction === DIRECTION_V ? DIRECTION_H : DIRECTION_V
        })
        // 滚动结束后派发事件
      if (this.pullup) {
        this.scroll.on('scrollEnd', () => {
          if (this.scroll.y <= (this.scroll.maxScrollY + MAX_BORDER_NUM)) {
            this.$emit('scrollToEnd')
          }
        })
      }
      this.scroll.on('scroll', (pos) => {
        if (pos.y > 30) {
          this.$emit('scroll')
        }
      })
      if (this.pullUpLoad) {
        this.scroll.on('touchEnd', (pos) => {
          if (pos.y > 30) {
            this.$emit('touchEnd')
          }
        })
      }
    },
    refresh() {
      this.scroll && this.scroll.refresh()
    },
    scrollTo() {
      this.scroll && this.scroll.scrollTo.apply(this.scroll, arguments)
    },

  },
  watch: {
    data() {
      setTimeout(() => {
        this.refresh()
      }, this.refreshDelay)
    }
  }
}
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">

</style>
